1. Field of the Invention
This invention relates to the field of encryption systems, and particularly to advanced encryption standard (AES) architectures.
2. Description of the Related Art
The advanced encryption standard (AES) is a new encryption standard which implements the Rijndael algorithm. The Rijndael algorithm accepts data blocks and key sizes of 128, 192, or 256 bits; the AES implementation is a symmetric block cipher with 128 bit data blocks and a key size that can be chosen from 128, 192, or 256 bits.
Several possible implementation modes of the AES standard are shown in FIG. 1. The AES algorithm may be employed as an electronic code book (ECB) which receives plaintext (P) and produces an encrypted output (C). The algorithm may also be employed in one of several feedback modes of operation; such feedback modes include Cipher Block Chaining (CBC), Cipher Feedback (CFB), and Output Feedback (OFB).
Ideally, an implementation of the AES standard will have a high data rate. Several AES designs have been proposed to achieve a high data rate based on pipelined architectures. These work well when employing the AES algorithm as an ECB, with no feedback. However, the AES standard is most often used in the feedback modes of operation; in these modes, the output of the AES algorithm is fed back to the input. Unfortunately, this arrangement is incompatible with pipeline structures, due to the long latency of each pipeline path.